Preparation and anti-inflammatory activity of triptolide ethosomes in an erythema model

Context: The aim of this work was to evaluate the suitability of ethosomes as carriers for the topical application of triptolide in a rat model of erythema. Objective: We determined the optimal conditions for preparing ethosomes, and we measured their vesicle size by a laser particle-size analyzer and the efficiency of entrapment of triptolide by ultracentrifugation. Methods: The in vitro percutaneous permeation of triptolide-loaded ethosomes was investigated by measuring diffusion across a sample of rat skin. To explore the transdermal delivery in vivo, we used a model in which erythema was induced in rats by methyl nicotinate and determined the change in erythema index caused by the anti-inflammatory activity of triptolide by a reflection spectrophotometer. Results: The optimal conditions for preparing triptolide ethosomes consisted of ultrasonication of 45% (v/v) ethanol and 2% (w/v) DPPC for 5 minutes, which produced an average vesicle size of 51.4 nm and an entrapment efficiency of 98%. This ethosomal formulation of triptolide caused the greatest in vitro 24-hour accumulation of triptolide (83.7%) with no permeation time delay, and it reduced erythema in vivo more rapidly and more completely than other formulations. Conclusions: Ethosomes might be a promising carrier that would enable the beneficial properties of triptolide to be safely delivered in a topical formulation.